Beyond average numbers of sea turtles have washed ashore in Southwest Florida beaches this year, and conservationists are worried about the possible impacts on this mass mortality on sea turtle populations. Experts suspect that the ongoing algal bloom is to blame for the deaths and illnesses.

Sea Turtle Mass Mortality

As of July 25, 91 stranded sea turtles have been recovered in the beaches around Sanibel and Captiva in Southwest Florida. In fact, 17 of the stranded were recovered just this past week.

On average, there are only between 30 and 35 strandings for an entire year, but there were over 50 strandings in June and July alone. Of the recovered sea turtles, 58 were already dead, while 33 were brought into custody to be given proper care. Further, 19 of the recovered turtles are Kemp’s Ridley sea turtles, a critically endangered species.

Red Tide To Blame?

Sea turtle researchers believe that the mass mortality is related to the ongoing red tide, which is evidently the longest algal bloom since the 2006 algal bloom that lasted for over a year So far, the current red tide has been ongoing for 10 months.

Although it is still not certain that the red tide is indeed responsible for the mass sea turtle mortality, evidence shows that many of the turtles exhibited neurological symptoms associated with red tide. Further, recent numbers show that the waters in Lee County reached levels of 1 million cells per liter when typically, fish kills and human breathing problems occur as a result of algal blooms with levels of 10,000 cells per liter.

Sea Turtle Population

Experts worry that the mass mortality can seriously dampen the conservation efforts for sea turtles. As mentioned, 19 of the recovered sea turtles are the critically endangered Kemp’s Ridley sea turtles, but also concerning is the fact that 53 of the affected turtles were mature adults. This may have a significant impact on sea turtle populations, especially since only 1 in 1,000 hatchlings survive until sexual maturity at between 25 and 30 years of age.

Evidently, red tide season typically ends by April, but the prolonged red tide this year collided with the sea turtles’ nesting season.

According to experts, the algal bloom likely causing the mass mortality is worsened by abnormally high amounts of nutrients that washed from the land and into the Gulf. As such, it is important to strengthen water quality standards to improve the currently dire conditions.

Karenia Brevis

Karenia Brevis is the organism responsible for the ongoing red tide. Although it is a naturally occurring organism, algal blooms may be intensified by poorer water qualities as a result of farming and development.

It is known for its toxicity because it produces brevetoxins that can cause mass mortalities in marine vertebrates and even human illnesses such as neurotoxic shellfish poisoning and respiratory irritation.